Calling a function inside a class to set the element of list

Question

I'm trying to implement my first class, partly as a way to break up the modeling and solving of a math problem I'm having trouble with. I don't think my problem relates to the class, but...?

The error keeps telling me that: "NameError: global name 'corner2' is not defined"

I tried moving the function call, but it still doesn't recognize it, so I put it back into the list declaration in my init function.

Here is my code:

class RotatedRectangle(object):

def corner1(a,b):
    a/=2
    b/=2
    x=(a-b)*math.sin(math.pi/4)
    y=(a+b)*math.sin(math.pi/4)
    return (x,y)

def corner2(a,b):
    a/=-2
    b/=2
    x=(a-b)*math.sin(math.pi/4)
    y=(a+b)*math.sin(math.pi/4)
    return (x,y)

def corner3(a,b):
    a/=-2
    b/=-2
    x=(a-b)*math.sin(math.pi/4)
    y=(a+b)*math.sin(math.pi/4)
    return (x,y)

def corner4(a,b):
    a/=2
    b/=2
    x=(a-b)*math.sin(math.pi/4)
    y=(a+b)*math.sin(math.pi/4)
    return (x,y)

def __init__(self, a, b,):
        """Return a Rotated rectangle object whose name is a function of a and b."""
        self.name = str(a) + "," + str(b) + "-rectangle"
        self.corners = [corner1(a,b), corner2(a,b), corner3(a,b), corner4(a,b)]



"""A rectangle with sides equal to even integers a and b is drawn on the          Cartesian plane.Its center (the intersection point of its diagonals) coincides with the point (0, 0),but the sides of the rectangle are not parallel to the axes; instead, they are forming 45 degree angles with the axes.

How many points with integer coordinates are located inside the given   rectangle (including on its sides)? """

score 2 · Answer 1 · answered Jul 04 '17 at 23:21

When defining methods for a class in Python, the first argument is usually set to "self". Then, when calling that method, prefix it with self.

Here is the working code:

import math

class RotatedRectangle(object):

    def corner1(self,a,b):
        a/=2
        b/=2
        x=(a-b)*math.sin(math.pi/4)
        y=(a+b)*math.sin(math.pi/4)
        return (x,y)

    def corner2(self,a,b):
        a/=-2
        b/=2
        x=(a-b)*math.sin(math.pi/4)
        y=(a+b)*math.sin(math.pi/4)
        return (x,y)

    def corner3(self,a,b):
        a/=-2
        b/=-2
        x=(a-b)*math.sin(math.pi/4)
        y=(a+b)*math.sin(math.pi/4)
        return (x,y)

    def corner4(self,a,b):
        a/=2
        b/=2
        x=(a-b)*math.sin(math.pi/4)
        y=(a+b)*math.sin(math.pi/4)
        return (x,y)

    def __init__(self, a, b,):
            """Return a Rotated rectangle object whose name is a function of a and b."""
            self.name = str(a) + "," + str(b) + "-rectangle"
            self.corners = [self.corner1(a,b), self.corner2(a,b), self.corner3(a,b), self.corner4(a,b)]

I think that's exactly the problem, plus one :) – developer_hatch Jul 04 '17 at 23:24 — developer_hatch, Jul 04 '17 at 23:24

score 1 · Answer 2 · answered Jul 04 '17 at 23:21

You have a few identation errors, and you forget to add the self parameter, it should be:

import math

class RotatedRectangle(object):
  def __init__(self, a, b,):
        """Return a Rotated rectangle object whose name is a function of a and b."""
        self.name = str(a) + "," + str(b) + "-rectangle"
        self.corners = [self.corner1(a,b), self.corner2(a,b), self.corner3(a,b), self.corner4(a,b)]

  def corner1(self,a,b):
      a/=2
      b/=2
      x=(a-b)*math.sin(math.pi/4)
      y=(a+b)*math.sin(math.pi/4)
      return (x,y)

  def corner2(self,a,b):
      a/=-2
      b/=2
      x=(a-b)*math.sin(math.pi/4)
      y=(a+b)*math.sin(math.pi/4)
      return (x,y)

  def corner3(self,a,b):
      a/=-2
      b/=-2
      x=(a-b)*math.sin(math.pi/4)
      y=(a+b)*math.sin(math.pi/4)
      return (x,y)

  def corner4(self,a,b):
      a/=2
      b/=2
      x=(a-b)*math.sin(math.pi/4)
      y=(a+b)*math.sin(math.pi/4)
      return (x,y)

I strongly recommend to you to read this question and all the answers What is the purpose of self?

Yeah, one thing I'm not loving about python. Copying and pasting seems to consistently cause indentation errors. Thank you for your response though. I will take on your suggested reading, it would seem there are parts of this class stuff I still didn't understand or wasn't familiar enough with. — Carl, Jul 05 '17 at 12:45
@Carl, you have to do it step-by-step. Don't forget mark the question as accepted and voting if was useful :) — developer_hatch, Jul 05 '17 at 12:50

score 1 · Accepted Answer · answered Jul 04 '17 at 23:41

You have to use self as the first parameter of your class methods
When calling class methods inside your class you have to pass self as their first parameter(so that the class knows that you are talking about the current object)

You have to indent when defining a method inside your class

import math
class RotatedRectangle(object):
    def corner1(self,a,b):
        a/=2
        b/=2
        x=(a-b)*math.sin(math.pi/4)
        y=(a+b)*math.sin(math.pi/4)
        return (x,y)

    def corner2(self,a,b):
        a/=-2
        b/=2
        x=(a-b)*math.sin(math.pi/4)
        y=(a+b)*math.sin(math.pi/4)
        return (x,y)

    def corner3(self,a,b):
        a/=-2
        b/=-2
        x=(a-b)*math.sin(math.pi/4)
        y=(a+b)*math.sin(math.pi/4)
        return (x,y)

    def corner4(self,a,b):
        a/=2
        b/=2
        x=(a-b)*math.sin(math.pi/4)
        y=(a+b)*math.sin(math.pi/4)
        return (x,y)

    def __init__(self, a, b,):
        """Return a Rotated rectangle object whose name is a function of a and b."""
        self.name = str(a) + "," + str(b) + "-rectangle"
        self.corners = [self.corner1(a,b), self.corner2(a,b), self.corner3(a,b), self.corner4(a,b)]

Calling a function inside a class to set the element of list

3 Answers3